寒地における水田雑草の出葉の温度反応とその地域性

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The effect of the water temperature on the leaf-emergence at the initial stage of the development in Echinochloa oryzicola VASING., Alisma canaliculatum A. BR, et BOUCHE and Scirpus juncoides ROXB. subsp. juncoides ROXB. under diurnal changes of water temperature was analyzed by measuring the effective cumulative water temperature. A method for the estimation of the progress of leaf-emergence in each type of weed depending on the region was developed based on the results obtained. 1. The coefficient of variation of the effective cumulative water temperature (Σ^<θ_w>) in each plot after sowing and before the leaf-emergence date depending on the diurnal variations of the water temperature was very small in comparison with the coefiicients of variation of the number of days required for emergence, and of the cumulative water temperature for the daily minimum, daily maximum and the average temperature (Table 5). 2. Based on these findings, it was considered that Σ^<θ_w> could be used as an index with high accuracy the progress of leaf-emergence in each type of weed under various conditions of water temperature including diurnal variations. Using Σ^<θ_w> the relationship between the diurnal variations of the water temperature and the progress of leaf-emergence of the weeds was quantified based on the type of weed and the depth of buried seeds (Fig. 5). 3. The variations in the date of emergence of the second leaf in each type of weed, associates with the changes of the date of the final puddling in a normal year in Sapporo, were analyzed. At the same time the data of emergence of the second and third leaves in each type of weed at 9 locations in Hokkaido was defined in relation to the changes of the air temperature of in a normal year. The number of days after the final puddling required for the emergence of the second leaf was the lowest (14 days) in Asahikawa for seeds of Echinochloa oryzicola buried at a depth of 0.2cm followed by Hakodate, Obihiro, Sapporo, Esashi, Rumoi, Muroran and Urakawa. The highest value (20 days) was recorded in Abashiri. When the daily mean temperature was 2℃ higher than in a normal year, the number of days advanced by 2 to 3 days. When the temperature was lower there was a delay of 3 to 4 days. In Abashiri in particular there was an increase in the differences in the numder of days required for the emergence of the second leaf depending on the depth of buried seeds. At the same time, leaf-emergence become irregular (Fig. 5). 4. The method for determining the effective cumulative water temperature is as follows. (1) The relationship between each constant for the water temperature (T) and the number s an or of days required for an increase of 0.2 leaves at the initial stage of growth of the weed (D) is represented by the equation: D= T/(-a+nT) (a and b are constants depending on the type of weed) (Fig. 1). (2) In the above-described equation T_a is estimated for the lowest value of T_I×D_I, and a_i satisfying the equation: a_1・T_1・D_1=a_2・T_2・D_2=……=a_n・T_n・D_n is derived by the equation : a_i=(T_a・D_a)/(T_i・D_i ') and then a_i・T_i is expected as θ_<wi> (effective water temperature) (Table 2). (3) Product summation of θ_w obtained for each value of water temperature with an increment of 2℃ and the time when the increment of the water temperature is observed, is calculated and adopted as the effective cumulative water temperature (Σθ_w) (Table 4).
日本雑草学会の論文
1987-08-31

寒地における水田雑草の出葉の温度反応とその地域性

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